Method of fabricating sealed containers



Oct. 24, 19390 J H PAYNE 2,177,498

METHOD OF FABRICATING SEALED CONTAINERS Filed Nov. 20, 1936 Ifivfib or"John H. Payne,

by 77 (SJ S I ZAttOT'WQy Pan -a ea. 24, 1939 PATENT OFFICE METHOD OFFABRICATING SEALED CONTAINERS John H. Payne, Ballston Spa, N. Y.,assignor to General Electric Company, a corporation of New YorkApplication November 20, 1936, Serial No. 111,828

2 Claims.

This invention relates to a method of fabricating sealed containers, andmore particularly for fabricating liquid contact switches of the'genera]type described and claimed in my copending application, Serial No.759,527, filed December 28, 1934, of which the present application is acontinuation in part.

The switches disclosed in my aforementioned copending applicationtypically comprise a closed vessel consisting of a pair of dished wallmembers of thin metal separated and insulated from one another by anapertured disk of non-conducting material, a quantity of mercurybeingprovided within the vessel to make and break an electrical circuitbetween the wall members. It is an object of the present invention tomake it possible for such switches to be manufactured econornically andunder conditions which substantially preclude the possibility ofdefective fabrication.

To this end I have provided a novel apparatusand mode of procedure bywhich the switch enclosing members may be accurately assembled andjoined with a minimum of human supervision. 1

The invention as a whole may best beunderstood by reference to thefollowing description taken in connection with the drawing, in whichFig. 1 is a perspective enlarged View showing certain of the switchparts in disassembled relationship; Fig. 2 is a plan view of apparatussuitable for the practice of the present invention; Figs. 3 to 8 arefragmentary views showing progressive steps in the switch assembly; andFigs. 9 and 10 illustrate the filling and sealing of assembled switchcontainers.

The switch assembly which has been chosen to exemplify the presentinvention comprises a refractory ceramic disk interposed between hollowmetal wall members, the nature and appearance of these elements beingwell illustrated in Fig. 1. The wall members Ill and it each comprise adished receptacle, typically of about'onehalf inch inside diameter,having an outwardly projecting flange thereon, such flanges beingnumbered l3 and M respectively. In order to facilitate mounting of theswitch each wall member is further provided with a central recess (seerecess I6) adapted to act as a socket for a cooperating supportingelement.

The size of the dished receptacles is such as to correspond quiteclosely with that-of a circular ceramic body or disk 18 which may beclamped between flanges l3 and I4. An aperture 19 formed in the diskpermits a closed electrical circuit to exist during certain positions orthe switch while the imperforate portions of the disk formcircuit-interrupting means during other positions. Accurate alinement ofthe wall enclosing wall members and the ceramic body as well as properorientation of the opening 19 after assembly are facilitated by means ofcoacting index notches 2| provided in each of the separable parts.

The ceramic disk and the wall members should be of such materials thatthey are capable of being joined and sealed by a thermoplastic materialfor example, a glass. For the ceramic I have successfully employed arefractory oxide mixed with vitriflable material, a suitable combinationbeing a mixture of about to per cent of magnesia and a complementaryproportion of clay. The metal parts may suitably comprise aniron-chromium alloy, a very satisfactory composition being one in whichthe chromium forms from 26 to 30 per cent of the alloy. As a preliminaryto the assembling process it is desirable to clean the metal parts witha grease solvent and to heat the flanges 13 and M with a gas flame todegas them and to oxidize the metal slightly. I

The assembling of the switch containers is car- 'ried out in accordancewith my invention by means of a multi-station fabricating apparatus suchas is illustrated in Fig. 2. This apparatus comprises, for example, arotary turntable 24 driven intermittently in such a way that each switchcontainer stops for a-definite interval at each of the circumferentiallyarranged stations (1, b, c, d, e, f, g, h, i and 7'. The operationsperformed at each of these stations will be set out more completely inthe following:

Stations a and b are loading stations at which the supervisory operatormay supply and position in proper relationship the principal elements ofthe switch assembly. These elements may for convenience be spread out ontrays 25 and 26 where they are readily accessible to the operator. Itwill be seen by reference to Fig. 3 that at station a the ceramic diskI8 is positioned between the metal enclosing members 10 and H, thesemembers being juxtaposed so that the flanges l3 and I4 extend outwardlybeyond the disk to form an outwardly open annular channel whose bottomis formed by the outer periphery of the disk. This preliminary assemblyis supported on the upper end of a hollow mounting or supporting memberwhich comprises a rounded cap 28 fitting into the depressed face of theswitch wall and which has an opening 29 communicating with an orifice 30in such wall. The cap 28 is supported by means of a hollow metal tube 32which is arranged to be vertically movable with respect to asupplemental mounting member 33 concentric therewith. This verticalmotion, which may be accomplished by a camming surface 36 operating onthe lower extremity of the tube 32, permits the relative elevation ofthe switch assembly to be modified from station to station in accordancewith the requirements of the various operations.

After the metal wall members and theceramic disk are initially assembledas indicated in Fig. 3 the turntable is rotated to bring this assemblyof parts to station b wherexthe supporting cap 28 is lowered so that theflange i 4 rests on the upper surface of the supplemental mountingmember 33. This member, which is suitably of graphite, affords a restfor supporting adjacent the juxtaposed edges of the enclosing members l0and H a premeasured quantity of glass, or other thermoplastic material,which is adapted to join with and seal the various switch parts. Aparticular material which has been found to be satisfactory for thispuipose comprises a commercial lead glass containing about 20 per centPbO and having a coeiiicient of thermal expansion of about x 10-centimeters per centimeter per degree centigrade. be provided in theform of a fillet or preferably a preformed closed ring 38 of such sizeas to be approximately co-extensive with theopening of the channel.

After the switch elements are positioned by the operator in the mannerindicated, the loose assembly of separable parts is moved onward to thevarious succeeding stations of the fabricating apparatus. At stations c,d, and e the parts are heated at a controllable rate, for example, bymeans of gas burners 39 provided at the stations. In order to bring thevarious elements up tohigh temperature by slow degrees so that excessivethermal stresses will be avoided, the flame temperatures of the variousburners may be progressively increased as one proceeds from station tostation. In addition the individual switch supports may be continuouslyrotated about their vertical axes to subject all parts to uniformheating, such rotation being accomplished, for example, by a gear 40secured to the member 33 as indicated in Fig; 5.

By the time the switch assembly as a whole has reached station e thering 33 will have become sufiiciently plastic so that it starts to flowunder the further application of heat. In order to controlthe nature ofits flow, it is desired to exert internal suction by the application ofa partial vacuum to the space enclosed by the switch wall members. Thismay be accomplished, for example, by connecting the tube 32 to a vacuumchamber adapted to exert the desired degree of suction. Connections forthis purpose are illustrated diagrammatically in Fig. 2, in which theconduits 42 shown in dotted outline comprise vacuum ducts running to thevarious vertical tubular supports 32 from a central chamber 43 which mayin turn be connected to a vacuum supply line 44. A combination ofstationary ports 45 and movable ports 46 which are controlled by therotation of the turntable 24 may be provided to secure the applicationor release of vacuum at any of the various operating stations. Thesuction thus developed may be communicated to the interior of the switchthrough the alined orifices 29 and 30 described in connection with Fig.3.

Such material may suitably 1 As shown in 1 1g. 6, which illustrates theconditions prevailing at station a, the progressive collapse of the ring38 will permit the thermo-. plastic material to be drawn into theannular channel defined between the flanges l3 and I4 5 and theperipheral urface of the ceramic disk l8.

If the various materials are properly related as specified in theforegoing description the final result will be to produce a hermeticseal between the thermoplastic material and the metal 10 wall membersand at least a liquid-tight seal between the thermoplastic material andthe ceramic disk. Under continued heating the soft- Fig. 8 'a particularmode of removal which has proven very satisfactory in actualpractice. A-'25 cording to the arrangement shown the completely assembled switchunit is subjected to a blast of air or other gas proceeding from anozzle 41 positioned adjacent the operating station i. It being assumedthat the vacuum has been removed 30 from the tube 32 at this station, arelatively slight air pressure is enough to topple the switch unit fromits mounting and to caus'" it to fall on to a suitable removal meansillustrated in Fig. 2 as a slide 49, whence it may be conducted tofurther 3:, processing apparatus. In the case illustrated this furtherapparatus comprises an annealing furnace 5| through which the completedswitches are carried on a continuous conveyor, such asa belt 52.

After such annealing and cleaning operations as are required theswitches may be filled with a desired amount oi. mercury or other liquidcontact medium. This procedure, which is illustrated in Fig. 9, maysuitably be accomplished 45 by means of an injection device 54 having aportion projecting through the opening 30 formed in the wall member N.Fig. 9 also shows each of the wall members as being provided internallywith a small insert 56 of contact metal. These 50 inserts may suitablycomprise iron finely coated with platinum and are of course providedbefore the assembly is begun. Their nature and utility are fullydescribed in an application, Serial No. 47,299 of W. R. Walker, filedOctober 29, 1935. 55 After the addition of a suitable amount of mercury53, the switch container may be permanentIy sealed, for example bywelding into the orifice 30 a plug of a difiicultly fusible metal suchas iron. The sealing operation, which may occur coinci- 60 dentally withthe injection of a protective gas into the switch container, is fullydescribed and claimed in my copending application, Serial No. 76,796,filed April 28, 1936. The nature of the sealing element is' indicatedgenerally in Fig. 10, in which it is shown as comprising a small plug 6|welded in place in the orifice 30.

While I have described my invention in con-.

nection with specific apparatus and a. definite 2,177,498 within thetrue spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of fabricating a hermetically sealed liquid contact devicecomprising a pair ispositively determined by said spacer, positioning apreformed solid glass member adjacent said flanges, said glass emberbeing coextensive with the opening of s d channel after assembly of thesaid members and spacer, and thereafter heating the said glass member tofusion temperature to fuse the same and producing a partial vacuumwithin the enclosure formed by said members and spacer to draw saidfused glass member inwardly into contact with the spacer while saidspacer maintains the spacing of said members constant.

2. The method of fabricating an electrical device comprising a pair offlanged metal enclosing members desired to be maintained electricallyseparated during at least certain conditions oi use of the device, whichmethod comprises positioning said members on opposite sides of aninsulating spacer with said flanges extending outwardly beyond saidspacer to provide an outwardly directed channel defined by the saidflanges and one surface of the spacer, placing about said channel apreformed conforming member of'solid thermoplastic material, heatingsaid material to fusion temperature to fuse the same and simultaneouslyproducing a partial vacuum within the enclosure formed by said membersand spacer until the fused thermoplastic material has been drawn intothe channel to form a seal between the members.

JOHN H. PAYNE.

